Energy Transfer in Metal–Organic Frameworks and Its Applications

Abstract

Photonic functional materials with designable and tunable energy transfer (EnT) processes have become increasingly popular as they significantly broaden the landscape of currently available luminescent materials. Metal–organic frameworks (MOFs), which are constructed from organic ligands and metal ions/clusters, possess highly ordered networks and tunable luminescent properties that make them excellent platforms for exploring EnT mechanisms and designing directional EnT processes. Although the EnT processes in MOFs have been extensively studied, the intricacies of the mechanisms between multiple emitting centers are still relatively unexplored. Thus, the rational design of tunable luminescent materials is quite arduous without a comprehensive understanding of these underlying mechanisms. In this review, the basic theories behind MOFs is systematically introduced from the perspective of the inherent EnT processes. The use of MOFs as ideal platforms for studying EnT processes and developing an efficient engineering strategy for enhancing luminescence and facilitating novel optical behaviors is highlighted. In addition, applications utilizing EnT in MOFs are emphasized, and the future prospects for the development of this technology are discussed.

Identification of Catalytic Active Sites for Durable Proton Exchange Membrane Fuel Cell: Catalytic Degradation and Poisoning Perspectives

“…The researchers have introduced several methods; in recent years, MOFs, as new porous materials, have gained extensive attention for several applications because of the well‐defined porous structure and highly ordered arrangement of organic linkers and metal nodes. [ 30,190–200 ]…”

“…The researchers have introduced several methods; in recent years, MOFs, as new porous materials, have gained extensive attention for several applications because of the well-defined porous structure and highly ordered arrangement of organic linkers and metal nodes. [30,[190][191][192][193][194][195][196][197][198][199][200] MOF-derived porous compounds, with high surface area, high stability, and flexible structures, are very promising candidates for ORR catalysis due to their inherited porous structures with large surface area and identical active sites after rational pyrolysis. [195,201] More importantly, their periodic structures give rise to spatial separation of building units and thus inhibit potential agglomeration of metal sites during pyrolysis, enabling MOFs as ideal precursors to create atomically dispersed active sites.…”

Applications of MOFs as Luminescent Sensors for Environmental Pollutants

“…[16,17] To date, the luminescent detection of LMOFs is essentially based on the mechanisms of charge and energy changes, such as aggregation-induced fluorescence enhanced (AIE), aggregation-induced quenching, distorted intramolecular charge transfer, bond energy transfer, and excited-state intramolecular proton transfer. [18,19] The detailed sensing mechanisms are shown as following: i) Photoinduced electron transfer (PET) is an electron transfer mechanism. The receptor connected to the fluorophore by the spacer can interact with analytes to achieve luminescent sensing (Figure 2a).…”

Directional Exciton Migration in Benzoimidazole-Based Metal–Organic Frameworks

“…Metal–Organic frameworks (MOFs) have been the center of attention in recent years due to their high design versatility and exceptional properties that have led to many potential applications in gas storage and separation, light-emitting devices, and fluorescent sensing. − This group of luminescent MOFs is particularly of great interest not only due to the wide range of emission wavelengths that can be obtained by tuning the MOF structure but also the excellent resistance to photobleaching. , Several mechanisms of the origin and quenching of fluorescence in these MOFs have been proposed and include ligand-centered emission, energy transfer from ligand to host or host to ligand, energy transfer from ligand to ligand, trapping in defect centers, and long-lived phosphorescence assisted by the presence of heavy metals. ,,− All these possibilities can be controlled by a selection of appropriate combinations of organic linkers and inorganic units, which contributes to the chemical structures of MOFs. ,, Among the proposed mechanisms, linker-to-linker energy transfer seems to be the most commonly used due to the facile way of controlling and tuning the optical properties of organic linkers through chemical-structure modifications. − ,− …”

“…1−4 This group of luminescent MOFs is particularly of great interest not only due to the wide range of emission wavelengths that can be obtained by tuning the MOF structure but also the excellent resistance to photobleaching. 1,5 Several mechanisms of the origin and quenching of fluorescence in these MOFs have been proposed and include ligand-centered emission, energy transfer from ligand to host or host to ligand, energy transfer from ligand to ligand, trapping in defect centers, and long-lived phosphorescence assisted by the presence of heavy metals. 1,2,5−11 All these possibilities can be controlled by a selection of appropriate combinations of organic linkers and inorganic units, which contributes to the chemical structures of MOFs.…”